AbstractThe sarcomeric myosin heavy‐chain (sMHC) gene of Drosophila is single‐copy and RNA transcription from this gene is developmentally regulated. Numerous sMHC mRNAs that differ in exon composition can be formed by alternate RNA processing. These transcriptional events result in the presence of multiple sMHC isoforms in the developing organism. We have developed and characterized two antibodies which are specific for different types of sarcomeric myosin heavy‐chain protein isoforms in Drosophila and have begun to examine the tissue distribution and function of these various protein isoforms. One of the antibodies (anti‐A) is capable of distinguishing between two classes of sMHC protein isoforms which differ in their carboxy terminal amino acid sequences. The second antibody (anti‐MHC) recognizes a separate and distinct domain in sMHC protein isoforms. We demonstrate the specificity and the utility of these antibodies in examining the developmental and tissue‐specific expression of sMHC protein isoforms in the developing fly.